1. Field of the Invention
The present invention relates to a drive motor for an electric vehicle and, more particularly, to a drive motor with a coolant passage for improving cooling efficiency.
2. Description of Related Art
Generally, an electric vehicle comprises a battery which is a source of electric energy and a drive motor which is supplied with electric energy from the battery to drive the vehicle.
When driving the vehicle, high-temperature heat is generated within the drive motor. Therefore, cooling means should be provided to cool the motor. The performance of the drive motor depends on the cooling efficiency of the cooling means.
FIG. 1 shows a perspective view of a conventional drive motor used in an electric vehicle.
As shown in FIG. 1, the drive motor comprises a cavity housing 10, a stator 11 around which a coil 12 is wound, the stator 11 being disposed within the housing 10, a rotor 13 disposed within the stator 11, and front and rear covers 14a and 14b for enclosing the hosing 10.
When electric power is applied to the coil 12 wound around the stator 11, the rotor 13 is rotated to drive the vehicle. At this point, high-temperature heat is generated within the motor. To cool the motor, coolant passages 15 are formed within the housing 10 and the front and rear covers 14a and 14b.
That is, as indicated by the arrows in FIG. 1, coolant is fed through an inlet port 16a formed on an upper surface of the front cover 14a, flows along the coolant passages 15 formed on the housing and front and rear covers 10, 14a, 14b, and finally is exhausted through an outlet port 16b formed in the upper surface of the front cover 14a. This circulation of the coolant is continuously performed, thereby cooling the drive motor.
However, in the above described conventional drive motor, since the coolant passages are formed in only four corners of the housing, the coolant cannot sufficiently cool the stator and coil, causing the motor to overheat.
In addition, the number of passages for circulation of the coolant makes it difficult to manufacture the motor. Furthermore, since the passages formed in the front and rear covers have to communicate with the coolant passages formed in the housing while maintaining a seal, a plurality of sealing members should be provided between the housing and the front and rear covers, making it difficult to assemble and disassemble the motor.